Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!feeder.erje.net!1.eu.feeder.erje.net!newsfeed.xs4all.nl!newsfeed8.news.xs4all.nl!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.001 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'cpython': 0.05; 'from:addr:yahoo.co.uk': 0.05; '*is*': 0.09; 'instruction.': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'wrong,': 0.09; 'python': 0.10; ':-)': 0.12; 'stack': 0.13; 'gregory': 0.16; 'iirc': 0.16; 'operation.': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'wrote:': 0.16; 'language': 0.19; 'explicit': 0.22; 'function,': 0.22; 'lawrence': 0.22; 'seems': 0.23; 'tried': 0.24; 'header:In-Reply-To:1': 0.24; 'wondering': 0.25; 'header:User-Agent:1': 0.26; "doesn't": 0.26; 'header:X-Complaints-To:1': 0.26; 'chris': 0.26; 'restrict': 0.27; 'assembly': 0.29; 'tail': 0.29; 'instruction': 0.29; "i'm": 0.30; 'subject:/': 0.30; 'code': 0.30; 'implement': 0.32; 'anybody': 0.32; 'language.': 0.32; 'jump': 0.33; 'languages': 0.34; 'too': 0.36; 'instead': 0.36; 'alone': 0.36; 'to:addr:python-list': 0.36; 'subject:: ': 0.37; 'received:org': 0.37; 'itself': 0.38; 'to:addr:python.org': 0.40; 'mark': 0.40; 'still': 0.40; 'ever': 0.60; 'charset:windows-1252': 0.62; 'our': 0.64; 'designers': 0.72; 'pythonistas,': 0.84; 'succeed.': 0.91 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Mark Lawrence Subject: Re: Possibly Pythonic Tail Call Optimization (TCO/TRE) Date: Wed, 15 Jul 2015 12:22:30 +0100 References: <55A3A853.4040006@rece.vub.ac.be> <55A3C366.6060602@rece.vub.ac.be> <87fv4r1fre.fsf@jester.gateway.sonic.net> <87bnff1eks.fsf@jester.gateway.sonic.net> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: host-78-146-4-131.as13285.net User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 In-Reply-To: X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.20+ Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 26 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1436959372 news.xs4all.nl 2893 [2001:888:2000:d::a6]:51249 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:93866 On 15/07/2015 10:13, Gregory Ewing wrote: > Chris Angelico wrote: >> I'm still interested in the explicit "replace current stack frame with >> this call" operation. Calling it "goto" seems wrong, as most languages >> with goto restrict it to _within_ a function, > > This just suggests to me is that most language designers > are not very imaginative. :-) > > A tail call *is* a goto. That's how you implement one in > assembly language -- you write a jump instruction instead > of a call instruction. The jump doesn't have to be to > the same function. > IIRC the realms of the C setjmp and longjmp. I'm just wondering out aloud if anybody has ever tried playing with cPython using these, or whether the code and/or Python itself is just too complex to allow this to even be tried, let alone succeed. -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence